California C-10 Electrical Contractor Exam
Practice Examination Questions With Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which California licensing classification is required to perform
electrical contracting work as a prime contractor?
A. B General Building Contractor
B. C-36 Plumbing Contractor
C. C-10 Electrical Contractor
D. C-39 Roofing Contractor
Rationale: The C-10 classification authorizes contractors to install,
alter, and repair electrical systems. Contractors performing electrical
work as a licensed specialty contractor in California generally require
the C-10 classification.
2. What is the primary purpose of the National Electrical Code
(NEC)?
,A. Reduce labor costs
B. Simplify contractor licensing
C. Provide minimum safety standards for electrical installations
D. Increase electrical consumption
Rationale: The NEC establishes minimum requirements for safe
electrical design, installation, and inspection to protect persons and
property from electrical hazards.
3. What color insulation is typically used for grounded conductors in
AC systems?
A. Green
B. Red
C. Black
D. White or gray
Rationale: The NEC identifies grounded conductors (neutrals) with
white or gray insulation or by specific marking methods.
4. Which instrument is commonly used to measure voltage?
A. Megohmmeter
B. Clamp meter
C. Phase rotation tester
D. Voltmeter
,Rationale: A voltmeter measures electrical potential difference
between two points and is an essential diagnostic tool for electricians.
5. What is the minimum working space depth in front of electrical
equipment rated 0–150 volts to ground under many standard
conditions?
A. 24 inches
B. 36 inches
C. 48 inches
D. 60 inches
Rationale: NEC working space requirements generally require a
minimum depth of 36 inches for many installations operating at 0–150
volts to ground.
6. Which law states that current equals voltage divided by
resistance?
A. Kirchhoff's Law
B. Faraday's Law
C. Coulomb's Law
D. Ohm's Law
Rationale: Ohm's Law is expressed as I = V ÷ R and forms the
foundation of electrical calculations.
, 7. What is the primary function of a circuit breaker?
A. Increase voltage
B. Reduce resistance
C. Protect conductors from overcurrent conditions
D. Improve power factor
Rationale: Circuit breakers automatically interrupt current flow during
overloads and short circuits, protecting equipment and conductors.
8. Ground-fault circuit interrupters (GFCIs) are designed primarily to
protect:
A. Equipment only
B. Motors only
C. Conductors only
D. People from electric shock
Rationale: GFCIs detect small leakage currents and quickly disconnect
power to reduce shock hazards.
9. Electrical continuity means:
A. High resistance
B. Open circuit condition
C. An uninterrupted path for current flow
D. Excessive voltage drop
Practice Examination Questions With Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which California licensing classification is required to perform
electrical contracting work as a prime contractor?
A. B General Building Contractor
B. C-36 Plumbing Contractor
C. C-10 Electrical Contractor
D. C-39 Roofing Contractor
Rationale: The C-10 classification authorizes contractors to install,
alter, and repair electrical systems. Contractors performing electrical
work as a licensed specialty contractor in California generally require
the C-10 classification.
2. What is the primary purpose of the National Electrical Code
(NEC)?
,A. Reduce labor costs
B. Simplify contractor licensing
C. Provide minimum safety standards for electrical installations
D. Increase electrical consumption
Rationale: The NEC establishes minimum requirements for safe
electrical design, installation, and inspection to protect persons and
property from electrical hazards.
3. What color insulation is typically used for grounded conductors in
AC systems?
A. Green
B. Red
C. Black
D. White or gray
Rationale: The NEC identifies grounded conductors (neutrals) with
white or gray insulation or by specific marking methods.
4. Which instrument is commonly used to measure voltage?
A. Megohmmeter
B. Clamp meter
C. Phase rotation tester
D. Voltmeter
,Rationale: A voltmeter measures electrical potential difference
between two points and is an essential diagnostic tool for electricians.
5. What is the minimum working space depth in front of electrical
equipment rated 0–150 volts to ground under many standard
conditions?
A. 24 inches
B. 36 inches
C. 48 inches
D. 60 inches
Rationale: NEC working space requirements generally require a
minimum depth of 36 inches for many installations operating at 0–150
volts to ground.
6. Which law states that current equals voltage divided by
resistance?
A. Kirchhoff's Law
B. Faraday's Law
C. Coulomb's Law
D. Ohm's Law
Rationale: Ohm's Law is expressed as I = V ÷ R and forms the
foundation of electrical calculations.
, 7. What is the primary function of a circuit breaker?
A. Increase voltage
B. Reduce resistance
C. Protect conductors from overcurrent conditions
D. Improve power factor
Rationale: Circuit breakers automatically interrupt current flow during
overloads and short circuits, protecting equipment and conductors.
8. Ground-fault circuit interrupters (GFCIs) are designed primarily to
protect:
A. Equipment only
B. Motors only
C. Conductors only
D. People from electric shock
Rationale: GFCIs detect small leakage currents and quickly disconnect
power to reduce shock hazards.
9. Electrical continuity means:
A. High resistance
B. Open circuit condition
C. An uninterrupted path for current flow
D. Excessive voltage drop
